# Error in Pyuavcan Demo **URL:** \ **Category:** PyCyphal\ **Created:** [April 7, 2021, 2:08am UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185 "2021-04-07T02:08:49Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Alanc](https://forum.opencyphal.org/letter_avatar_proxy/v4/letter/a/34f0e0/32.png) [@Alanc](https://forum.opencyphal.org/u/Alanc)\ **Post date:** [April 7, 2021, 2:08am UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/1 "2021-04-07T02:08:49Z")
Hey guys, I am new to all this and I am trying my best to learn by going through tutorials but I ran into an error when following along with the Pyuavcan Demo. I am using windows PowerShell, and python 3.9 and this error happened when I was trying to run Demo\_app can someone help explain why this error appeared? ![image](https://forum.opencyphal.org/uploads/default/original/1X/f561113c6e3b35d4bf44ed5f47f8ced2b66d7535.png) My end goal by learning all this is to develop a way of daisy chaining multiple Pixhawks through CAN Bus for a project of mine, if you have any insight or tips on this that would be greatly appreciated! ---
**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\ **Post date:** [April 7, 2021, 11:03am UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/2 "2021-04-07T11:03:47Z")
Hi Alan, This is the intended behavior of the demo. The very next sentences say: > If you just run the script as-is, you will notice that it fails with an error referring to some _missing registers_. > … > So the application fails with an error that says that it doesn’t know how to reach the UAVCAN network it is supposed to be part of because there are no registers to read that information from. We can resolve this by passing the correct register values via environment variables ---
**Author:** ![Alanc](https://forum.opencyphal.org/letter_avatar_proxy/v4/letter/a/34f0e0/32.png) [@Alanc](https://forum.opencyphal.org/u/Alanc)\ **Post date:** [April 7, 2021, 1:42pm UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/3 "2021-04-07T13:42:51Z")
Hey Pavel, Thanks for the response and sorry I should have been a little more specific but I did input the correct register values via environment variables, how they say to in the demo but I still got the same error? ---
**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\ **Post date:** [April 7, 2021, 1:44pm UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/4 "2021-04-07T13:44:25Z")
Can you please share the CLI dump here? ---
**Author:** ![Alanc](https://forum.opencyphal.org/letter_avatar_proxy/v4/letter/a/34f0e0/32.png) [@Alanc](https://forum.opencyphal.org/u/Alanc)\ **Post date:** [April 7, 2021, 2:49pm UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/5 "2021-04-07T14:49:45Z")
Yes, so here is what I have been doing I state my register values and then run the demo app, ![image](https://forum.opencyphal.org/uploads/default/original/1X/2744c533abecd334d9ef2faddf0d595a9248db63.png) ---
**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\ **Post date:** [April 7, 2021, 3:39pm UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/6 "2021-04-07T15:39:57Z")
I think it’s a syntactic peculiarity of PowerShell. Try taking each value in double quotes: ```auto $env:UAVCAN __UDP__ IFACE="127.9.0.0" ``` ---
**Author:** ![Alanc](https://forum.opencyphal.org/letter_avatar_proxy/v4/letter/a/34f0e0/32.png) [@Alanc](https://forum.opencyphal.org/u/Alanc)\ **Post date:** [April 7, 2021, 3:58pm UTC](https://forum.opencyphal.org/t/error-in-pyuavcan-demo/1185/7 "2021-04-07T15:58:07Z")
It’s working! Thank you, I appreciate the help !